A gas turbine is provided with a compressor that compresses air, a combustor that combusts fuel in the air compressed by the compressor and generates combustion gas, and a turbine that is driven by the combustion gas from the combustor.
Examples of the combustor include a combustor provided with a dual-fuel nozzle that selectively sprays oil fuel, such as light oil, and gas fuel, such as natural gas. In this type of combustor provided with the dual-fuel nozzle, when the oil fuel remains in an oil fuel channel of the nozzle after switching the fuel to be used from the oil fuel to the gas fuel, coking of the oil fuel may occur under a high-temperature environment. When the coking of the oil fuel occurs in the oil fuel channel, the oil fuel channel becomes narrower, making it difficult to cause the oil fuel to flow through the oil fuel channel at an intended flow rate.
Thus, in a technology disclosed in Patent Document 1 described below, after the switching from the oil fuel to the gas fuel is completed, water is intermittently supplied to the oil fuel channel a plurality of times. After that, air is supplied to the oil fuel channel to remove the oil fuel remaining in the oil fuel channel, thereby inhibiting the coking of the oil fuel from occurring in the oil fuel channel.